Embodiments of the invention are directed to a laser system having switchable power modes. Other embodiments are directed to a method of operating the laser system using a laser pump module having switchable power modes.
High power laser systems have a broad range of applications throughout the scientific, industrial and medical fields. Laser systems generally include a pump module, a gain medium and a laser resonator. The pump module includes laser diodes or bars that generate pump energy. The gain medium absorbs the pump energy and emits laser light responsive to the absorbed energy. The laser resonator operates to generate a harmonic of the laser light.
The pump energy can be applied to the gain medium from the side of the gain medium, known as side-pumping, or from the end of the gain medium, known as end-pumping. Side-pumping is relatively inefficient; so that the conversion of pump energy into laser output is low at relatively high pump energies. End-pumping is more efficient. However, an upper limit is quickly reached for end-pumped gain media, where rapid absorption of pump energy in a small volume within the first few millimeters of the gain media causes thermal fracture.
The gain medium is generally tuned to absorb pump energy having a wavelength that is within a specified operating band. Thus, the wavelength of the pump energy must be carefully controlled to ensure proper operation of the laser system.
The wavelength of the pump energy varies with a temperature of the laser diodes and the current supplied to the laser diodes. Such fluctuations in the wavelength of the pump energy can be readily controlled when the pump energy is operated at a continuous power level and sufficient time is allowed for the system to reach a steady-state temperature. However, some applications of laser systems desire multiple power laser output modes and the ability to rapidly switch among the power output modes while maintaining the excellent pump absorption efficiency at all power modes. Such rapid switching between different power output modes by varying the pump current can cause the pump energy to stray outside the operating band of the gain medium causing low pump energy to lasing energy conversion efficiency, which can potentially damage the pump source by unabsorbed pump energy.